Use a fixed globally unique meeting ID, fixes #734

Removed the option to randomize meeting IDs, now they are fixed and
generated as a globally unique meeting ID. #745
Use meetingID to match recordings instead of metadata, fixes #735

Now we have globally unique IDs so we can use the meetingID to match
recordings, so the attribute 'uniqueid' in BigbluebuttonRoom is no longer
required.
Add .ruby-version